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Building Basics/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim watches as Moby stacks blocks unevenly. TIM: Hey Moby, I don't think that's gonna stand up. MOBY: Beep. Tim reads from a typed letter. TIM: Dear Tim and Moby, How are buildings made? From, V.C. An image shows city buildings. TIM: Well, all buildings have to fight against the force of gravity. An image illustrates gravitational force as Tim describes it. TIM: Gravity pulls everything on the surface towards the center of the earth. So any structure we build has to resist a force that wants to pull it down. Moby places a block on top of his block tower and the tower falls. MOBY: Beep. TIM: Well, for a structure to stay up, it has to work with the forces of compression and tension. MOBY: Beep. Moby squeezes the ends of a loaf of bread together. TIM: Compression is a force that squeezes matter together. When matter is compressed, it gets shorter. Moby stretches a rubber band. TIM: And tension is just the opposite: it's a force that pulls the material apart. When matter is in tension, it gets longer. Some things we build stay up pretty easily, without any internal structure. One of the most basic structures is the post and lintel. You can find one of the simplest examples of the post and lintel at Stonehenge, in England. An image shows Stonehenge, England. TIM: In a post and lintel structure, two vertical columns support a horizontal beam. Two vertical stones are each labeled "post." The horizontal stone is labeled "lintel." TIM: When weight is applied to the beam, it starts to bend, compressing the columns. The whole thing works together to support the weight of the load. But the post and lintel isn't just for holding up big stones. An animation shows an arrow pointing down, indicating how the weight in the center of the beam makes it bend. The posts under the ends of the beam stop it from bending. TIM: You can see the post and lintel at work in something as simple as a doorway. An animation shows a doorway's hidden post and lintel structure. An arrow in the center points downward to show how the posts support the weight of the beam and the forces pushing against it. MOBY: Beep. TIM: Here, the post and lintel structure supports the weight of the wall on top of the doorway. The post and lintel isn't the only structure that can support a lot of weight without internal supports. Moby is shown building his block tower. An arrow points to the bottom blocks. TIM: When Moby tried to build a tower earlier, all the weight was put on one block. That's not a very sturdy construction. MOBY: Beep. TIM: But if we build a pyramid, the weight of the blocks is distributed on a wider base, which stabilizes the structure. Moby rearranges the blocks into a pyramid shape. TIM: This is how the pyramids in Egypt were built, and it's part of the reason they've stayed up for so many thousands of years. An image shows the Great Pyramids in Egypt. TIM: Pyramids can be as tall as they are because they rest on a really wide base that can support the weight of all the stone. The wider the base, the higher you can build the structure. Imagine if the pyramids were five times as tall. An animation shows that a tall pyramid would need a very wide base. TIM: The base of the pyramid would have to be enormous to support all that height. Pyramids and posts and lintels are good for simple buildings, but eventually people had to figure out better ways of keeping structures up. When you get into suspension bridges and skyscrapers, it gets a whole lot more complicated, but it's always good to know the basics. MOBY: Beep. Moby holds a detailed drawing of "Moby Cathedral." TIM: Um, I think you're going to need more blocks for that, Moby. MOBY: Beep.Category:BrainPOP Transcripts Category:BrainPOP Engineering & Technology Transcripts Category:BrainPOP Science Transcripts